Terrorism concerns arise as Prince Harry, Meghan Markle nuptials near

LONDON -- As the Royal Wedding gets closer, concerns arise over possible terrorist attacks that could happen.

Five terrorist attacks plagued London, making 2017 a brutal year for the city. Just outside the castle in Windsor, there are constant reminders of heavy security as armed officers and bomb sniffing dogs patrol the area.

"Since 2016, there have now been 45 separate attacks across several European countries," said Andrew Parker, MI5 director general.

MI5, Britain's counterintelligence and security agency, said it has stopped a number of terror plots.

"In the UK alone since the Westminster attack in March last year, with the police we've thwarted a further 12 Islamist terror plots. Twelve occasions where we have good reason to believe a terrorist attack would otherwise have taken place in our country. That brings the total number of disrupted attacks in the UK since 2013 to 25," Parker said.

As many as 100,000 people could line streets outside of the castle on Saturday, with road closures, police barriers, license plate recognition systems and snipers just being part of the event.